Treating hydrocarbon distillates



NOV. 5, 194D. C* WHQTHy 3D 2,220,697

TREATING HYDROCARBON DISTILLATES Filed Mar'ch 51, 1939 in many instances.

Patented Nov. 5, 1940 UNiTED STATES PATENT OFFICE TREATING HYDROOARBON DISTILLATES Appiication March 31, 1939, Serial No. 265,069

` v 12 Claims.

the methods which have been used is the sulfuric acid treating method forv improving color, reducing sulfur content, and improving storage stability of cracked gasolines. Another method makes use of the refining eiects of adsorbent materials using natural earths of the clay type, such as fullers earth, which may or may not be activated by chemical treatment. Therening action of the so-called clay treating process is carried out with the gasoline in either vapor or liquid phasedepending on the temperature and pressure conditions used. This method has Wide application, particularly in connection with gasolines of low sulfur content. It is with improvements in this type of process r,that the present invention is concerned.

In one specic embodiment my invention comprises fractionating the vaporous products from a cracking process into a distillate of substan.

tially gasoline boiling range, separately accumulating a portion of said distillate to use as reux vmaterial in said fractionation step, treating said reiiux condensate with an acidic substance, such as dilute mineral acid; separating and returning it t'o the ractionating column, passing the'total products of distillation to a clay treat-x ing step operated under treating conditions, land recovering the iinishedgasoline.

Certain distillates resist' treatment with a sorbent rening agents so that low yields of nished gasoline per unit weight of treating reagent are obtained, and the processV is not v`economical. Formerly such distillates were treated with sulfuric acid, but since the speciiications for gasolines have changed in recent years, the more severe acid treatment is no longer required Its use with certain distillates has been continued' by many renners, Ahowever, because no other economical method was available and these distillatesrequired treatment in some form 'before they could be marketed. It has been found that the treatment of such refractory gasolines withv dilute acid or other acidic substances prior to the clay vtreating step vresultsin improvementin yields to an ,extent suchv that the operation becomes Ooi a practical nature. The preferred reagent comprises'. dilute. sulfuric'A acid, normally of 1-20% concentration, although other mineral acids, acid sulfates, and solutions of heavy metal halides may be used satisfactorily by varying the treating conditions somewhat. The treateddistillates may or may not be neutralizedprior to the clay treating step. This particular method of operation has resulted in improvements, but has one disadvantage in that the entire distillatemust bev condensed, subjected to the acid -'treating step, and then reheated to the desired treating temperature for the clay treating step. This is disadvantageous when the vapor phase clay treating process isemployed, since one of the advantages of vapor phase clay treating lies in the fact that gasoline vapors are treated directly w fromthe main fractionator of the cracking plant. The improvement of the present invention comprises the method for realizing the advantages of both acidpretreatment and vapor-phase clay treatment. q

In the fractionation it is necessary to return a portion of the overhead distillate to the top of the fractionator 'as reflux to assist in controlling the top'temperatu're of the fractionator and the end point of the product being taken overhead. The portion of the product which is used as reiiux varies in quantity from equal parts to approximately four times the amount of distillate which is actually taken overhead, depending on the composition of the'material being fractionated and upon the design ofthe fractionating equipment., The reux condensate must becooled and pumped in liquid form to the top of the fractionator in order to obtain the desired lresult. It is possible to effect considerable im provement in the treating operation by contacting this reflux condensate, which amounts to Sil-'75% of the total product, with dilute acid prior to returning it to the fractionation step, and as ^`a. consequence, extend the life of the. adsorbent earth in the treating tower materially. At the same time, it is not necessary to supply additional cooling or heating to the gasoline beyond lthat which is normally used in the fractionation step alone. The amount of treatment obtained in this way is suicient to improve the life of the clay at -no additional cost beyond the' chemicals used and the equipment necessary to carry out the pretreatment. The amount of acidic solution used-is' dependent toa certain extent on the concentration of the-treating solution and may vary from'1-10% ormore by volume of the distillate. The concentrations of the acidic substance are normally less Athan 20% although this varies with the solumally the acid strength should be kept belowthat at which ysludge formation occurs. Phosphoric acid may b used in similar concentrations. Hydrochloric acid should be used in con-- centrations of less than 10% in order to avoid undesirable chlorination of the gasoline.

The clay treatment may be carried out in any 2 distillate may vbe withdrawn from the frac-4 suitable apparatus employing "temperaturesof 25o-600, F. andpressures of substantially atmospheric to 100 pounds when'employing the vapor phase process. The treated gasoline may 15 or may not require fractionation in order to produce an end point product. The -steps of treating with clay `and recovering the treated gasoline are well known and need' not be ldiscussed in detail. l

'I'he attached diagrammatic drawing shows No attempt --one embodiment of the invention. v

has been made to proportionate the various parts of the apparatus and no scale has been used in the drawing. 'I'he process should not be'inter-4 preted as beingrestricted tothe exact equipment or flow given.

The vapors from the cracking plant enter the i fractionator through line I and valve 2, passing into the main fractionator 3 where the heavy recycle oil is withdrawn through line 4 and valve -5 and returned to the cracking plant. Accordingto the preferred method of operation the gases and the vapors o f'substantially gasoline boiling range leave the top of the fractionator a5 through line 6 and pass through line 1 and valve 8. A portion of the vapors then are passed through .line 9, valve I0, and condenserV II, line I2 and valve I3 into the reux`accumulator. I4; From thence it is withdrawn-through." line .I5, valve I6 by means of pump I1, valve I8 into the acid Washing system I9. The acid solution en ters the plant through line 20 and valve 2i and the spent solution is withdrawn from the acid washer through line 22 and valve 23. The .acid

- '45 washing system may'comprise any suitable' arrangement but is preferably ofthe countercur. rent type whereby maximumvuse of the acid isf obtained. Furthermore, the partially spent acid may be 'recirculated if desired by means not shown. The=gasoline leaves the system through line 24 and valve 25 and may pass through valve' 26 into neutralizer 21 where it may' bewashed with water or with an alkaline solution to remove any residual acid remaining. In this case the neutralized gasoline passes out through line 28 yand valve 29 to line 30 and passes thence to the 'top of the fractionating column as reux. In 'this case the water or neutralizing solutionc enters-the plant through line 3| and valve 32 and 00 line- 33 which joins with line 24. The spent solution may be withdrawn'thrpugh line 34 and valve 35. As in the case of the acid washer any suitable apparatus may be use d for this purpose and the ineutralizing solution may be recirculated by means not shown. :In son'ie cases the neutralization step can be dispensedwith. Iny

this case the neutralizer isby-passed by means .of line 33, valve 36 and line 31 which joins with line -30. Gases which are separated in reflux 7.0 accumulator I4 may be withdrawn from the rev ceiver through line' 38 and valve 39, or if ldesired they may be passed together with the gasoline intothe clay treating system by means o f `line 4.0.and valve 4I which loins with Vline-42.

' u` The portion of the distillate which is not passed tionator through lin `e 1, valve 8, line 42 and valves 43 and 44 directly to the treating tower. The heavy portion of the gasoline is taken through line 48 andvalve 49, a portion passing ll through line 42 and valve 43 to the treating system, while the remainder which is to be used as reflux condensate is passed through line 9, valve I0 and routes previously described through the acid\treating step. and returned as reux 2| vcondensate to the top of the fractionator.

In still another alternative a -side cut is withdrawn thrigh line 43 and valve l49 as'just de scribed, and a light overhead fraction is taken through lines 6 and 50 and valve 5I. In certain 2l instances this fraction requires no treatment and may be blended directly with the finished treated gasoline. In other casesa light treatment with -the dilute acidmay be given thel low boiling fraction in a separate acid washing system which 3l is not shown but which may be similar to the one used for the reflux condensate. ,It is `oftentimes the practicewhen treating by ythe vapor phase clay method to remove distillate4 from the fractionator with'a somewhat' higher 3l 'end point than the finished gasoline. The end Q.

point of the gasoline-is 'then adjusted by the fractionation step wherein `the polymers are separated following the clay treatment. Since the gasoline is to Areceive a final fractionation I for adjusting the end point, it is not necessary that the fractionation in the main fractionator be a's exact as might otherwise be thev case. 'This makes possible the alternative` methods described above wherein a naphtha side cutis used"4l as reflux material in the fractionator.

described according to the preferred method in 5l the foregoing specifications. The end point of 'the' overhead material from the main fractionator was approximately 420 Rand a reflux ratio d of approximately 3:1 was used. This means that 3 parts of reflux condensate were collected, treated with dilute acid, condensed and returned to the top of the fractionating column, to 1 part of gasoline passed to the clay treating system. The refiuxcondensate was treated with 21/2% by volume' oi' 10%v sulfuric acid, separated and washed 65 with 5% of 5% sodium hydroxide solution and returned to the fractionator. The .total mixture of reaction products from the clay treating step was fractionated to produce a 400 F'.v end point gasoline. In thismanner a yield lof- 2300 barrels 7i" oi gasoline having aI 25 color, oxygen bomb in.- duction period of 150 minutes and 25 mg. of copper dish gum per cc, was 'produced per ton" of clay. The induction period of the gasoline was increased to 355 minutes and the gum lowered to m 5 mg. by the addition of 0.0025% of a commercial inhibitor. By running to a color of 21 Saybolt the yield obtained was increased to 3800 barrels p'er ton of clay. When operating on this particular distillate in the usual manner Without the pretreatment of the reflux condensate a yield of only 900 barrels per ton of clay was obtained. Fullers earth was used as the treating reagent and the gasoline was contacted at a temperature of 450 F. and 50 pounds per square inch pressure at the inlet to the clay tower.

I claim as my invention:

1. A process for refining hydrocarbon distillate which comprises fractionating said distillate into a fraction of substantially gasoline boiling range, collecting a portion of said gasoline as reux condensate, treating said condensate with an acidic rening agent and returning it as reux to the fractionator, passing a portion of the fractionated gasoline vapors to a refining stepv and therein contacting-the same with an adsorbent refining agent, and recovering the refined gasoline.

2. The process of claim 1 wherein the ratio of reux condensate to gasoline passed to the .adsorbent refining agent is between the limits of approximately 1:1 and 4:1.

3. The process of claim 1 wherein the secondmentioned refining agent is any adsorbent clay.

4. The process of claim 1 wherein the acidic refining agent is a mineral acid.

5. The process of claim 1 wherein 'the acidic rening agent comprises essentially sulfuric acid.

6. A process for refining gasoline which comprises fractionating said gasoline into high and low boiling fractions, recovering said low'boiling faction Without further refining, contacting a portion of said high boiling fraction with an adsorbent refining agent, accumulating another portion of the high boiling gasoline fractions from the fractionating step, condensing and contacting said accumulated gasoline with an acidic refining agent, separating it, and then returning it to the fractionating step as reux, continuously withdrawing the products from the adsorbent treating step, and recovering the gasoline therefrom.

7. A process for rening gasoline which comprises fractionating said gasoline into low and high boiling fractions, contacting said low boiling fraction and a portion of said high boiling fraction with an adsorbent treating reagent, recovering the gasoline therefrom, accumulating another portion of said high boiling gasoline fraction from the fractionation step, condensing and contacting it with an acidic refining agent, and separating and returning the thus treated oil to the fractionation step as reflux..

8. A refining process which comprises fractionating hydrocarbon vapors containing gasoline and heavier hydrocarbons to separate the gasoline from heavier hydrocarbons, passing a portion of 'the gasoline in vapor form from the fractionating step to a refining step and therein contacting the same with an adsorbent refining agent, treating another portion of the gasoline from the fractionating step with an acidic refining agent and thereafter returning 'it in liquid form to the fractionating step -as a reiluxing medium therein.

9. A refining process which comprises fractionating hydrocarbon vapors containing gasolineA and heavier hydrocarbons to separate the gasoline from heavier hydrocarbons, removing the separatedk gasoline from the fractionating step in vapor form, contacting a portion o'f theA gasoline vapors with an adsorbent refining agent, condensing another portion of the gasoline vapors and treating it with an acidic refining agent, and returning the thus treated condensed gasoline to the fractionating step las a refluxing medium therein.

10. A rening process which comprises fractionating gasoline-containing vapors to form a light vaporous gasoline fraction and a condensate containing heavier gasoline fractions, contacting said vaporous fraction with adsorbent clay, treating said condensate with an acidic refining agent and thereafter returning it to the fractionating step as a refluxing medium therein.

1l. A rening process which comprises fractionating hydrocarbon vapors containing g-asoline and heavier hydrocarbons to separate the gasoline from heavier hydrocarbons, passing a p portion of the gasoline in vapor 'form from the fractionating step to a refining step and therein contacting the same with adsorbent clay, treating another portion of the gasoline from the fractionating step with a dilute mineral acid solution and thereafter returning it in liquid form to the fractionating step as a refluxing medium therein.

12. A refining process which comprises fractionating hydrocarbon vapors containing gasoline and heavier hydrocarbons to separate the gasoline from heavier hydrocarbons, passing a portion of the gasoline in vapor form from the fractionating step to a refining step and therein contacting the same with adsorbent clay, treating another'portion of the gasoline from the" fractionating step with a dilute sulfuric acid solution and thereafter returning it in liquid form to thefractionating step as a.v refiuxing medium therein.

CHARLES WIRTH, DI. 

